Functional fluid compositions

ABSTRACT

FUNCTIONAL FLUID COMPOSITIONS OF THE CLASS WHICH EXHIBIT THE ABILITY TO INHIBIT AND CONTROL DAMAGE TO MECHANICAL MEMBERS IN CONTACT WITH SAID COMPOSITIONS BY THE INCORPORATION OF HEAVY WATER INTO A CLASS OF BASE STOCKS REPRESENTATIVES OF WHICH ARE THE ESTERS AND AMIDES OF PHOSPHORUS, THE ORTHO-SILICATES, THE POLY-SILICONES, THE ARYL ETHERS AND ESTERS. THESE COMPOSITIONS HAVE MANY USES, AMONG WHICH ARE THEIR USE AS HYDRAULIC FLUIDS.

United States Patent 01 3,630,916 Patented Dec. 28, 1971 3,630,916 FUNCTIONAL FLUID COMPOSITIGNS Quentin Elwyn Thompson, Belleville, lll., assignor to Monsanto Company, St. Louis, M0. N Drawing. Filed July 21, 1966, Ser. No. 566,735 Int. Cl. (109k 3/00; ClOm 3/40 U.S. Cl. 252-78 19 Claims ABSTRACT OF THE DISCLOSURE Functional fluid compositions of the class which exhibit the ability to inhibit and control damage to mechanical members in contact with said compositions by the incorporation of heavy water into a class of base stocks representatives of which are the esters and amides of phosphorus, the ortho-silicates, the poly-silicones, the aryl ethers and esters. These compositions have many uses, among which are their use as hydraulic fluids.

This invention relates to functional fluid compositions having an ability to inhibit and control damage to mechanical members in contact with said fluid compositions, to functional fluid compositions which exhibit an improved tendency to resist fluid degradation, to functional fluids which have improved resistance to acid buildup and more particularly to compositions comprising certain func tional fluids and an additive amount, suflicient to inhibit and control damage, of heavy water.

Many different types of materials are utilized as functional fluids and functional fluids are used in many different types of applications. Thus, such fluids have been used as electronic coolants, atomic reactor coolants, diffusion pump fluids, lubricants, damping fluids, bases for greases, power transmission and hydraulic fluids, heat transfer fluids, heat pump fluids, refrigeration equipment fluids and as filter mediums for air conditioning systems. In many of these uses there have been reports of damage to the fluid during use and to mechanical members, especially metallic members, in contact with the fluid as evidenced by a loss of weight of such members. Thus, damage has been reported in aircraft hydraulic systems, gas turbine bearings, jet turbine control systems, steam turbine bearings and steam turbine control systems. Damage has also been observed on such materials as glass, Teflon, Mylar, Plexiglas and other members constructed from materials other than metals.

One particularly undesirable condition which exists during the use of a functional fluid and which can cause damage is cavitation, which can be described as a phenomenon which results in the formation and subsequent violent collapse of vapor-filled bubbles in a fluid subjected to requisite pressure changes. Bubbles can be formed when the fluid is at or below its bubble point pressure; above this pressure they collapse. Pressure changes sufficient to cause cavitation can occur in several ways; for example, a fluid flowing through a restriction, such as a partially closed valve, can encounter at the point of highest velocity a pressure far lower than both the bubble point and the valve outlet pressures thus resulting in bubble formation. As these bubbles reach a point of high pressure, for example on the discharge side of the valve, a violent collapse of the bubbles occurs thereby producing shock waves which can be severe enough to damage the fluid and mechanical members in contact with the fluid. As another example, caviation conditions can occur when a surface is moved through or vibrated in a relatively stagnant liquid.

While there are many undesirable results caused by damage, one important aspect of the problem of damage is the effect on hydraulic systems and fluids experiencing such damage. For example, the structural mechanical parts in a hydraulic system, such as pumps and valves, exhibit a marked decrease in strength, and the geometry of the parts is altered. Such changes in the case of pumps can cause a decrease in pumping efliciency and in the case of valves can cause faulty operations, excessive leakage or even hazardous conditions. As a result, damage ne cessitates premature overhaul of mechanical parts which is both costly and time consuming. In addition, as damage occurs the metal from metallic mechanical parts in contact with the functional fluid contaminates the fluids requiring premature draining of the fluids from the sys tem, filter clogging and excessive filter replacement, and can cause a change in physical and chemical properties of the fluids. Also, metal contaminants can reduce the oxidative stability of a fluid thereby adversely affecting fluid performance. In addition to any effects resulting from contamination by metal (or other) contaminant, such damage to the fluid can manifest itself in numerous Ways, among which are (a) viscosity change, (b) increase in acid number, (0) formation of insoluble materials, ((1) increased chemical reactivity and (e) discoloration.

It is, therefore, an object of this invention to provide functional fluid compositions having an ability to inhibit and control damage.

It is a further object of this invention to provide functional fluid compositions having an ability to inhibit and control damage and retain the critical properties of the functional fluid used to provide such compositions.

Further objects will be apparent from the following description of the invention.

It has now been found that damage, herein defined to include damage to a functional fluid and to mechanical members in contact with said fluid, can be effectively controlled and inhibited in the many functional fluid systems described by the incorporation of heavy water, and mixtures thereof. Heavy water is herein defined to include water which contains any isotope of hydrogen, any isotope of oxygen or any combination of isotopes of oxygen and hydrogen. It is an important part of this invention that the incorporation of heavy Water in functional fluids produces a functional fluid composition having the ability to inhibit damage without adversely affecting the other critical properties of such fluids such as viscosity, oxidative and thermal stability, corrosion resistance in the presence of metal parts and lubricating qualities of the functional fluid.

Typical examples of heavy water are HOD, D 0, HO D, D 0 HO D, D 0 and mixtures thereof. The functional fluids, to which heavy water is added to pro vide the compositions of this invention, hereinafter referred to as base stocks, include, but are not limited to, esters and amides of an acid of phosphorus, hydrocarbon materials including both hydrocarbon materials derived from petroleum sources and synthetic hydrocarbon oils, hydrocarbyl silicates, silicone-s, ether compounds which include polyphenyl ether compounds, polyphenyl thioether compounds mixed polyphenyl ether-thioether compounds, phenoxybiphenyl compounds, phenylmercaptobiphenyl compounds, mixed phenoxyphenylmercapto biphenyl compounds and the above ether compounds in which part or all of the phenyl and phenylene rings are replaced with a heterocyclic group such as thiophene or pyridene, monoand di alkylthiophenes, chlorinated biphenyl, monoesters, diand tricarboxylic acid esters, esters of polyhydric compounds, complex esters and mixtures thereof.

The concentration of heavy water in the functional fluid is adjusted in terms of the particular system and the functional fluid which is utilized in this system to prospawns vide functional fluid compositions of this invention which contain additive amounts of heavy water surficient to inhibit and control damage. Thus. it has been found that the additive response, that is, the concentration of heavy water required to inhibit and control damage, of a base stock varies according to the base stock or blends of base stocks. Thus, for the base stocks of this invention the concentration of heavy water is from about 0.005 volume percent to about 15 volume percent, the particular concentration being that amount which will effectively inhibit and control damage. The preferred additive concentration is from about 0.10 volume percent to about 5 volume percent of heavy water, although 0.005 volume percent to about 10 volume percent have been found satisfactory and effective to inhibit and control damage. Therefore, included within the present invention are compositions comprising a functional fluid and a damageinhibiting amount of heavy water, that is, heavy water is added, in a concentration sufficient to control and inhibit damage. The functional fluid compositions of this invention can be compounded in any manner known to those skilled in the art for the incorporation of an additive into a base stock as for example by adding heavy water to the base stock with stirring until a homogenous fluid composition is obtained.

The esters and amides of an acid of phosphorus which are suitable as base stocks for the functional fluid compositions of this invention are those represented by the structure where Y is selected from the group consisting of oxygen, sulfur and its Y is selected from the group consisting of oxygen. sulfur and and Y is selected from the group consisting of oxygen, sulfur and R, R R R R and R are each selected from the group consisting of alkyl, aryl, substituted aryl and substituted alkyl wherein R, R R R R and R each can be identical or different with respect to any other radical, X is selected from the group consisting of sulfur and oxygen and a, b and c are whole numbers having a value of 0 to l and the sum of a+b+c is from 1 to 3.

Typical examples of alkyl radicals are as follows: methyl, ethyl, normal propyl, isopropyl, normal butyl, isobutyl, secondary butyl, tertiary butyl, normal amyl, isoamyl, 2-methylbutyl. 2,2dimethyl propyl. l-methyl butyl, diethyl methyl, 1,2-dimethyl propyl, tertiary amyl, normal hexyl, l-methylamyl, l-ethyl butyl, 1,2,2-trimethyl propyl, 3,3-dimethyl butyl, 1,1.2-trimethyl propyl, 2-methyl amyl, 1,1-dimethyl butyl, l-ethyl Z-methyl propyl, 1,3-dimethyl butyl, isohexyl, 3-methylamyl, l,2-dimethyl butyl, l-methyl l-ethyl propyl, Z-ethyl butyl, normal heptyl l,l,2,3-tetramethyl propyl, 1,2-dimethyl l-ethyl propyl, 1,1,2-trimethyl butyl, l-isopropyl Z-methyl propyl, l-methyl Z-ethyl butyl, 1,1-diethyl propyl, Z-methyl hexyl, l,l-dimethyl amyl, l-isopropyl butyl, l-ethyl 3-methyl butyl, 1,4-dimethyl amyl, isoheptyl,

l-methyl l-ethyl butyl l-ethyl l methyl butyl, l-methyl hexyl, lpt'opyl butyl, normal octyl, l-methyl heptyl. l.ldiethyl 2-rnethyl propyl, l,l,3,3-tetramethyl butyl, 1,1-

4 diethyl butyl, 1,1-dimethyl hexyl, l-methyl l-ethyl amyl, l-methyl l-propyl butyl, 2-ethyl hexyl 6-methyl heptyl liso-octyl), normal nonyl, l-methyl octyl, l-ethyl heptyl, 1,1-dimethyl heptyl, l-ethyl l-propyl butyl, 1,1-diethyl S-methyl butyl, diisobutyl methyl, 3,5,5-trimethyl hexyl, 3.5-dimethyl heptyl, normal decyl 1-propyl heptyl, 1,1- diethyl hexyl, 1,1-dipropyl btttyl, 2-isopropyl S-methyl hexyl and C alkyl groups.

It is also contemplated within the scope of this invention that all or part of the hydrogen other than hydrogen occupying the one position in the previously described alkyl radicals can be replaced by halogens, such as fluorine, chlorine or bromine.

It is also contemplated that the above alkyl and halogenated alkyl groups can have oxa linkages linking any two carbon atoms contained in the alkyl and halogenated alkyl groups.

Typical examples of aryl and substituted aryl radicals are phenyl, cresyl, xylyl, halogenated phenyl, cresyl and xylyl in which the available hydrogen on the aryl or substituted aryl is partially or totally replaced by a halogen, o-. mand p-trifluoromethylphenyl, o-, mand p- 2,2.2trifluoroethylphenyl, 0-, mand p-3,3,3-trifluoropropylphenyl and o-, mand p-4,4,4-trifluorobutylphenyl.

The preferred esters of an acid of phosphorus are those base stocks wherein a, b and c have a value of 1, Y, Y and Y are oxygen and R, R and R are alkyl, aryl or substituted aryl. Typical examples of these esters of an acid of phosphorus, that is, phosphates, are dibutylphenyl phosphate, triphenyl phosphate, tricresyl phosphate, tributyl phosphate, tri-Z-ethylhexyl phosphate, tri octyl phosphate and mixtures of the above phosphates, such as mixtures of tribtttyl phosphate and tricresyl phosphate. and mixtures of isooctyldiphenyl phosphate and l-ethylhexyldiphenyl phosphate and mixtures of trialkyl phosphates and tricresyl phosphates and the like.

The preferred amides of an acid fo phosphorus are those wherein j, k and I have a value of l and K, Y and Y are selected from oxygen and respectively. Typical examples of the amides of an acid of phosphorus, that is, mono-, diand triamides of an acid of phosphorus, hereinafter defined as phosphoroamidates, are

phenyl-methyl-N,N-dimethyl-phosphoroamidate; phenyl-rnethyl-N,N-di-n-butylphosphoroamidate; mixtures of phenyl-m-cresyl-N,N-dimethylphosphoroamidate and phenyl-p-cresyl-N,N-dimethylphosphoroamidate; mixtures of m-cresyl-p-cresyl-N,N-dimethylphosphoroamidate, di-m-cresyl-N.N-dimethylphosphoroamidate and di-p-cresyl-N,N-dimethylphosphoroamidate; di-m-bromophenyl-N-methyl-N-n-butylphosphoroamidate; di-m-chlorophenyl-N-methyl-N-n-butylphosphoroamidate; di-ot,a,a-triflttoro-n1-c1'esyl-N-methyl-N-n-butylphosphoroamidate; di-p-bromophenyl-N-metltyl-Nn-isoamylphosphoroamidate; di-p-chlorophenyl-N-methyl-N-n-isoumylphosphoroamidate; p-chlorophenyl-m-bromophenyl-N-methyl-N-n-isoztntylphosphoroamidate; phenyl-N-methyl-N-butyl-N'-mcthyl-N-butylphosphorodiamidate; phenyl-N,N-di-n-butyl-N,N'-di-n-butylphosphorodiamidate; phenyLNQMdimctltylN',N'-tlimclh lpliospliorodiamidate;

m-chlorophenyl-N-methyl-N-n-butyl-N'-methyl-N'-nbutylphosphorodiamidate; m-bromophenyl-N-methyl-N-n-butyl-N'-methyl-N'-nbutylphosphorodiarnidate; m,a,a-trifluoro-m-cresyl-N-methyl-N-n-butyl-N'-methyln-butylphosphorodiamidate; p-chlorophenyl-N-methyl-N-isobutyl-N'-methyl-N'- isoamylphosphorodiamidate; p-bro-mophenyl-N-methyl-N-isobutyl-N'-methyl-N- isoamyl-phosphorodiamidate; N-methyl-N-butyl-N-rnethyl-N-butyl-N"-methyl-N"- butylphosphorotriamidate; N-methy1-N-butyl-N,N"-tetramethyl-phosphorotriamidate; N-di-n-propyl-N'-N'-tetramethylphosphorotriamidate;

and N,N-di-n-propyl-N"-dimethylphosphorotriamidate.

Typical examples of phosphinate esters are phenyl-di-n-propyl phosphinate, phenyl-di-n-butyl phosphinate, phenyl-di-sec-butyl phosphinate, phenyl-di-n-pentyl phosphinate, phenyl-di-neopentyl phosphinate, phenyl-di-n-hexyl phosphinate, phenyl-di-n-butyl thiophosphinate, p-methoxyphenyl-di-n-butyl phosphinate, m-chlorophenyl-di-n-butyl phosphinate, phenyl-(n-propyl-n-pentyl) phosphinate, phenyl-(n-propyl-n-butyl) phosphinate, phenyln-propyl-n-hexyl) phosphinate, phenyln-butyl-n-pentyl) phosphinate, phenyl-(n-butyl-n-hexyl) phosphinate, phenyl-(n-pentyl-n-hexyl) phosphinate, phenyl-(neopentyl-n-propyl) phosphinate, phenyl-(neopentyl-n-butyl) phosphinate, phenyl-(neopentyl-n-hexyl) phosphinate, thiophenyl-di-n-propyl phosphinate, thiophenyl-di-n-pentyl phosphinate, cresyl-di-n-pentyl phosphinate, tert-butylphenyl-di-mbutyl phosphinate, n-butyl-phenyl-di-n-butyl phosphinate, sec-butylphenyl-di-n-butyl phosphinate, ethylphenyl-di-n-butyl phosphinate, xylyl-di-n-butyl phosphinate, thiophenyl-di-n-hexyl phosphinate, thiophenyl-di-n-butyl phosphinate, thiophenyl-di-n-propyl thiophosphinate, thiophenyl-di-n-butyl thio phosphinate, thiophenyl-di-n-pentyl thiophosphinate, thiophenyl-di-n-hexyl thiophosphinate, thiophenyl-(n-propyl-n-butyl) phosphinate, thiophenyl-(propyl-n-pentyl) phosphinate, thiophenyl-(n-propyl-n-hexyl) phosphinate, thiophenyl-(n-butyl-n-pentyl) phosphinate, thiophenyl-(n-butyl-n-hexyl) phosphinate, thiophenyl-(n-pentyl-n-hexyl) phosphinate, thiophenyln-propyl-n-butyl) thiophosphinate, thiophenyl-(n-propyl-n-pentyl) thiophosphinate, thiophenyl-(n-propyl-n-hexyl) thiophosphinate, thiophenyl-(m-butyl-n-pentyl) thiophosphinate, thiophenyl-(n-butyl-n-hexyl) thiophosphinate and thiophenyl-(n-pentyl-n-hexyl) thiophosphinate.

The orthosilicates useful as base stocks include the tetraalkyl orthosilicates such as tetra(octyl)orthosilicates, tetra(Z-ethylhexyl)orthosilicates and the tetra(isooctyl) orthosilicates and those in which the isooctyl radicals are obtained from isooctyl alcohol which is derived from the x0 process, and the (trialkoxysilico)trialkyl orthosilicates, otherwise referred to as hexa(alkoxy) disiloxanes, such as hexa(2-ethylbutoxy) disiloxane and hexa(2- ethylhexoxy) disiloxane.

The preferred tetraalkyl orthosilicates and hexa- (alkoxy) disiloxanes are those in which the alkyl or alkoxy radicals have from 4 to 12 carbon atoms and in which the total number of carbon atoms in the ortho- -silicate is from 16 to 60.

In addition to the hexa(alkoxy) disiloxanes referred to above, other hexa(alkoxy) disiloxanes can be used in which the aliphatic radical of the alkoxy groups are for example, l-ethylpropyl, 1,3-dirnethylbutyl, Z-methylpentyl, l-methylhexyl, l-ethylpentyl, 2butylhexyl and 1-methy1-4-ethyloctyl.

The orthosilicates and alkoxy polysiloxanes can be represented by the general structure wherein R R and R each can be alkyl, substituted alkyl, aryl, substituted aryl and can be identical or different With respect to any other radical, O is oxygen, Si is silicon, X is a member of the group consisting of carbon and silicon, m is a whole number having a value of 0 or 1, n is an integer having a value of from 1 to about 200 or more and when X is carbon m is O, n is l and R R and R each can be hydrogen, alkyl, substltuted alkyl, aryl and substituted aryl radicals and when X is silicon m is l, n is an integer having a value of from 1 to about 200 or more and R R and R each can be alkyl, substituted alkyl, aryl and substituted aryl.

Typical examples of substituted aryl radicals are 0-, mand p-chlorophenyl, o-, mand p-bromophenyl, o-, mand p-fluorophenyl, a,u,a-trich1orocresyl, a,a,u-trifiuoro cresyl, xylyl and o-, mand p-cresyl. Typical examples of alkyl and haloalkyl radicals are those heretofore described.

The siloxanes or silicones useful as base stocks are represented by the general structure wherein R R R R R and R can each be alkyl, substituted alkyl, aryl and substituted aryl radicals and n 1s a whole number from about 0 to about 2000 or more. Typical examples of alkyl and haloalkyl radicals are those heretofore described. Typical examples of the siloxanes are poly (methyl) siloxane, poly(methyl, phenyl) siloxane, poly (methyl, chlorophenyl)siloxane and poly- (methyl, 3,3,3-trifluoropropyl)siloxane.

Typical examples of substituted aryl radicals and o-, mand p-chlorophenyl, 0-, mand p-bromophenyl, o-, mand p-fluorophenyl, a,a,a-trichlorocresyl, a,u,u-trifluorocresyl, o-, mand p-cresyl and xylyl.

Diand tri-carboxylic acid esters which are suitable as base stocks are represented by the structure wherein 0, 0, p and p each are whole numbers having the value of O to 1 provided that the sum of each of o+p and o'+p' is 1; A is a whole number having a value of l to 2; R and R each can be alkyl, cycloalkyl, substituted alkyl, alkenyl, substituted alkenyl, aralkyl, sub stituted aralkyl, aryl and substituted aryl; and R can be a hydrocarbon radical and a substituted hydrocarbon radical. Typical examples of alkyl, aryl, substituted alkyl and substituted aryl radicals are given above.

Typical examples of diand tricarboxylic acid esters are di(Z-ethylhexyl) azelate, di(2-ethylhexyl) sebacate, diisooctyl sebacate, Z-ethylhexyl 3:5 :5 trimethylhexyl sebacate, diisooctyl azelate, di(3 :5 5 trimethylhexyl) sebacate, di( 1- methyl-4-ethyloctyl) sebacate, diisodecyl azelate, diisotridecyl azelate, di( l-methyl-4-ethyloctyl) glutarate, di(2- ethylhexyl) adipate, di(3-methylbutyl) azelate, di(3:5:5 trimethylhexyl) azelate, di(2-ethylhexyl)adipate, di(C (O "ill; R C O cll tflL it wherein R is selected from the group consisting of hydrogen and alkyl, R and R are each selected from the group consisting of alkyl, substituted alkyl, cycloalkyl, aralkyl, aryl and substituted aryl, a is a whole numher having a value of to 1, a is a whole number having a value of 0 to 1, Z is a whole number having a value of l to 4 and when Z is l a is 0 and R is selected from the group consisting of acyloxy and substituted acyloxy and when Z is 2 to 4 u is l and R is selected from the group consisting of acyl and substituted acyl.

Typical polyester compounds can be prepared by the reaction of acid compound with a polyhydroxy compound which polyhydroxy compound can be trimethylolpropane, trimethylolethane, pentaerythritol. dipentaerythritol, tripentaerythritol and tetrapentaerythritol.

The acids which may be utilized are aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, aromatic monocarboxylic acids and heterocyclic monocarboxylic acids, such as propionic, butyric. isobutyric, n-valeric, caproic, n-heptylic, caprilic, Z-ethylhexanoic, 2,2-dimethylheptanoic and pelargonic. Examples of esters of this type are esters of trimethylolpropane (1 mole) with monocarboxylic acids (3 moles), e.g., trimethylolpropane tri-noctanoate; esters of pentaerythritol 1 mole) with monocarboxylic acids (4 moles); esters of dior tripentaerythritol (1 mole) with monocarboxylic acids (6 or 8 moles). Typical examples of alkyl, substituted alkyl, aryl and substituted aryl radicals are given above.

Other esters which are also suitable as base stocks are hydrocarbon monoesters containing one ester group. typical examples of which are isooctyl stearate and Z-ethylhexyl octoate.

Complex esters which are suitable as base stocks are represented by the structure wherein R and R are each selected from the group consisting of hydrogen. alkyl. substituted alltyl. alkenyl, substituted alkenyl. aryl. substituted aryl, cycloalkyl, Substituted cycloalkyl and a carbocyclic radical containing from 6 to carbon atoms: R and R are each selected from the group consisting of tlltylene. substituted alkylene. alkenylene. substituted alkenylene. phenylcne and substituted phenylene: is a whole number having a \alue from 1 to about 80.

Typical examples of complex esters can he obtained by esterifying dicarboxylic acids with a mixture of monohydric alcohol and a glycol to give complex esters. Complex esters which can be employed can be prepared by estcrifying a dicarbtnylic acid I l molet with a glycol (2 moles) and a monocarboxylic acid 12 moles) or tuth 1 mole each of a glycol. a dicurbou lie and and a monohydric alcohol or with 2 moles each of a monohydroxy monocarboxylic [lClLl and a monohydric alcohol. Still other complex esters may be prepared by esterifying a glycol (1 mole) with a monohydroxy monocarboxylic acid (2 moles) and a monocarboxylic acid (2 moles).

Other complex esters which are suitable as base stocks are prepared by polymerizing a dihydroxy compound with a dicarboxylic acid and reacting the terminal hydroxy and acid radical with a mixture of a monocarboxylic acid and a monohydric alcohol. Specific examples of polymers which may be utilized as additives within the scope of this invention are polymers prepared by the polymerization of adipic acid and 1,2-propane diol in the presence of minor amounts of short-chain monocarboxylic acids and a monohydric alcohol to give molecular weights of the polymers thereby produced of from about 700 to about 40.000 or higher.

The mono-. diand polyhydric alcohols, and the monocarboxylic acids employed in the preparation of the complex esters can also contain ether oxygen linkages.

Specific examples of suitable complex esters are esters prepared from methylene glycol (1 mole), adipic acid (2 moles) and Z-ethylhexanol (2 moles); esters prepared from tetraethylene glycol (1 mole), sebacic acid (2 moles). and Z-ethylhexanol (2 moles); esters prepared from Z-ethyl-l:3 hexanediol (1 mole), sebacic acid (2 moles) and Z-ethylhexanol (2 moles); esters prepared from diethylene glycol (1 mole), aclipic acid (2 moles) and n-butanol (2 moles); esters prepared from polyglycol 200 1 mole). sebacic acid (2 moles) and ethylene glycol monotZ-ethylbutyl) ether (2 moles); esters prepared from sebacic acid (1 mole), tetraethylene glycol 42 moles) and caproic acid (2 moles); esters prepared from triethylene glycol (1 mole) adipic acid (1 mole), n-caproic acid (1 mole) and Z-ethylhexanol (1 mole); ester prepared from sebacic acid (1 mole), lactic acid (2 moles) and n-butanol (2 moles); esters prepared from tetraethylene glycol (1 mole), lactic acid (2 moles) and butyric acid (2 moles); complex esters prepared front neopentyl glycol (2 moles), dicarboxylic acids (1 mole) and monocarboxylic acids (2 moles) and complex esters prepared from neopentyl glycol (1 mole) dicarboxylic acids (2 moles) and monohydric neoalcohols, e.g., 2,2,4- trimethylpentanol (2 moles).

Another class of base stocks which are suitable as base stocks for this invention are represented by the structure where A. A A and A are each a chalkogen having an atomic number of 8 to 16; each q is a whole number having a value of l to 5; each r is a whole number having a value of l to 4: X. X X X and X each are selected from the group consisting of hydrogen, alkyl, haloalkyl. halogen. arylalkyl and substituted arylalkyl, .r. and z are whole numbers each having a value of t) to 8 and is a whole number having a value of O to 1 provided that when a is 0. y can have a value of l to 2. Typical examples of alkyl and substituted alkyl radicals are given above. Typical examples of such base stocks are 2- to 7-ring ortho-. metaand para-polyphenyl ethers and mixtures thereof. 2- to 7-ring ortho-. metaand parapolyphcnyl thioethers and mixtures thereof. mixed polyphcnyl etherthtocther compounds in which at least one of the chalkogens represented by A, A A and A is dissimilar with respect to any one of the other chalkogens, dihalogenated diphenyl ethers, such as 4-bromo-3'-chlorodiphenyl ethers and bisphenoxybiphenyl compounds and mixtures thereof. It is also contemplated within the scope of this invention that the phenyl and phenylene groups in the aforedescribed aromatic ether compounds can be partially or totally replaced by a heterocyclic group such as thiophene or pyridene. Such heterocyclic groups can contain from 4 to atoms optionally interrupted by from 1 to 4 hetero atoms such as oxygen, nitrogen and sulfur.

Examples of the polyphenyl ethers contemplated are the bis(phenoxyphenyl) ethers, e.g., bis(m-phenoxyphenyl) ether, the bis(phenoxyphenoxy)benzenes, e.g., m-bis m-phenoxyphenoxy) benzene, m-bis p-phenoxyphenoxy benzene, o-bis (o-phenoxyphenoxy benzene, the bis(phenoxyphenoxyphenyl) ethers, e.g., bis[m- (mphenoxyphenoxy)phenyl] ether, bis[p (p phenoxyphenoxy)phenyl] ether, m-[(m-phenoxyphenoxy) (o-phenoxyphenoxy)] ether and the bis(phenoxyphenoxyphenoxy)benzenes, e.g., m-bis[m (m-phenoxyphenoxy)phenoxy]benzene, p-bis[p (m phenoxyphenoxy)phenoxy]- benzene, m-bis (m-p-phenoxyphenoxy phenoxy] benzene and mixtures thereof with other polyphenyl ethers.

Typical examples of polyphenyl thioethers and mixed polyphenyl ethers and thioethers are Z-phenylmercapto-4-phenoxydiphenyl sulfide, 2-phenoxy-3-phenylmercaptodiphenyl sulfide, o-bis phenylmercapto benzene, phenylmercaptobip-henyl, bis(phenylmercapto)biphenyl, m-(m-chlorophenylmercapto)-m-phenylmercaptobenzene, phenylmercapto(phenoxy)biphenyl, m-ehlorodiphenyl sulfide, bis(o-phenylmercaptophenyl) sulfide, m-bis(m-phenylmercaptophenylmercapto) benzene, 1,2,3-tris(phenylmercapto)benzene, 1-phenylmercapto-2,3-bis(phenoxy)benzene, o-bis (o-phenylmercaptophenylmercapto benzene, m-bis(p-phenylmercaptophenylmercapto)benzene, 2,2-bis phenylmercapto diphenyl ether, 3 ,4'-bis( m-tolylmercapto diphenyl ether, 3,3'-bis(xylylmercapto)diphenyl ether, 3 ,4'-bis m-isopropylphenylmercapto diphenyl ether, 3,4'-bis( p-tert-butylphenylmercapto diphenyl ether, 3 3'-bis m-chlorophenylmercapto )diphenyl ether, 3,3-bis m-trifluoromethylphenylmercapto diphenyl ether, 3,4-bis(m-perfluorobutylphenylmercapto)diphenyl ether, Z-m-tolyloxy-2'-phenylmercaptodiphenyl sulfide, o-bis phenylmercapto benzene, bis m-phenylmercaptophenyl) sulfide, m-phenylmercaptophenyl-p-phenylmercaptophenyl sulfide,

the trisphenylmercaptobenzenes such as 1 ,2,4-trisphenylmercaptobenzene,

3,3-bis(phenylmercapto)diphenyl,

m-bis p-phenylmercaptophenylmercapto) benzene,

m-bi s m-phe nylme rcaptophenylmercapto benzene,

bis mm-phenylmercaptophenylmercapto phenyl] sulfide,

3 ,3 '-bis phenylmercapto) diphenyl ether,

3,3 '-bis phenoxy diphenyl sulfide,

3-phenoxy-3-phenylmercaptodiphenyl sulfide,

3-phenylmercapto-3'-phenoxydiphenyl ether,

3 ,4'-bis (phenylmercapto diphenyl ether,

m-bis m-phenylmercaptophenoxy )benzene,

3-phenylrnercapto-3-(m-phenylmercaptophenylmercapto)diphenyl ether.

Other base stocks which are useful are monoand dialkylthiophenes. Typical examples of thiophenes are 1 0 2,5 l-hexyll-methylnonyl thiophene, 2,4- l-hexyll-methylnonyl thiophene, 2-tert-butyl thiophene, 2,5-tert-butyl thiophene, 2,5 1, l-dimethylpropyl thiophene, 2,5 l-butyll-octylnonyl thiophene, 2,5 l -propylcyclobutyl thiophene, 2-tert-butyl-4-(-1-octyl-l-methyloctadecyl)thiophene, 2,5 l-methylcyclohexyl thiophene, 2,5 l-octyll-methyldecyl) thiophene, 2,5-(1,l-dimethyltridecyl)thiophene, 2, 3-( l, l-dimethyltridecyl) thiophene, 2,4-( 1,1-dimethyltridecyl) thiophene, 2,4-( l-methylcyclopentyl thiophene, and 2,5 l-n-dodecylpentyl thiophene.

Hydrocarbon materials, including both hydrocarbon materials derived from petroleum sources such as, for example, mineral oils, fuel oils and kerosene types and synthetic hydrocarbon oils, are suitable base stocks. The physical characteristics of functional fluids derived from a mineral oil are selected on the basis of the requirements of the fluid systems and therefore this invention includes as base stocks mineral oils having a wide range of viscosities and volatilities such as naphthenic base, paraffinic base and mixed base mineral oils. In addition, lower boiling hydrocarbon material, such as fuel oil and kerosene types, are often pumped at pressures whereby pump surfaces can be damaged, such as the pumping of jet fuels and these fuels are included within the term hydrocarbon materials.

The synthetic hydrocarbon oils include but are not limited to those oils derived from oligomerization of olefins such as polybutenes and oils derived from high alpha olefins of from 8 to 20 carbon atoms by acid catalyzed dimerization and by oligomerization using trialuminum alkyls as catalysts.

Another base stock which is suitable is chlorinated biphenyl. It is also contemplated within the scope of this invention that mixtures of individual compounds which are included in a generic type of base stock can be utilized as a base stock within the scope of this invention. For example, two different polyesters can be blended together to form a base stock. In addition, it is contemplated Within the scope of this invention that the various generic types of base stocks can be blended together to form base stocks. Thus, a mixture of S-ring polyphenyl ethers can be blended with a polycarboxylic acid ester to form a base stock.

An additional example of the use of various generic type base stocks which can be blended together to form a base stock is a base stock prepared by blending from about 10% to about 50% of a hydrocarbon oil with from about 30% to 60% of a chlorinated biphenyl and from about 5% to about 25% of an ester of acid of phosphorus such as a triarylphosphate. In addition, it is contemplated that other additives and materials such as blending agents can be added to the above base stocks. Thus, for example, a blending agent such as trior tetrachlorobenzene can be added to the above mixture comprising a hydrocarbon oil, an ester of an acid of phosphorus and a chlorinated biphenyl.

The invention can be better appreciated by the following non-limiting examples. In Examples 1 through 4 a nickel specimen was immersed in a test fluid and a 20 kilohertz vibration induced into the specimen. The test duration was 45 minutes. In all the following examples, the temperature during the test was C. Relative weight loss is defined to mean the total weight loss of the metal specimen when tested in the fluid containing the additive present divided by the weight loss of the metal specimen when the fluid is tested without any additive present times 100. Thus, a relative weight loss under indicates that less metal was removed from the specimen when the additive was present in a given base stock and therefore demt1 onstrates that the fluid compositions which incorporate heavy water inhibit and control damage.

The test method as employed to determine relative damage has been found to correlate quite well to actual test runs on simulated hydraulic system test stands. such as the Fairey Test Stand. The Fairey Test Stand is a closed loop hydraulic system wherein the test conditions simulate the actual fluid pressures and temperatures as would exist on an aircraft. Such test stand has been in use for the purpose of testing hydraulic fluids and hydraulic components. In addition, the hydraulic system test stands for determining damage have correlated quite well with the hydraulic system of commercial aircraft where damage levels have been determined.

Similar results are obtained with other types of heavy water such as HOD, HO D, D 0 HO D and D 0 An additional test was run to determine the acid build up of water versus heavy water. The test consisted of placing 200 ml. of a fluid sample into a stainless steel bomb in which was stacked metal test samples which were aluminum, cadmium, copper. iron and magnesium. The bomb was rotated at 300 F. for a period of 72 hours. In Table II the base stock that was used was dibutylphenyl phosphate. Percent reduction in acid number was determined by the following formula:

Percent z'eduction No. H O minus Acid No. Heavy at? 100 T Acid NOT iiio TABLE II Percent itltl X0. wluction It has generally been found that the above bomb test correlates quite well with actual conditions to which a hydraulic fluid is subjected. This test has found utility for the evaluation of high temperature hydraulic fluids, which temperatures are presently being encountered in actual hydraulic systems.

The data in Table I and Table II demonstrate the significant inhibition of damage obtained by the incorporation of heavy Water into a base stock and the relative decrease in acid build-up using a composition of this invention. In addition, the critical physical properties and the critical performance characteristics such as lubricity, fire resistance, and viscosity are not adversely affected by the additive, an important consideration since a base stock is selected for a given fluid system because of its physical properties or characteristics and deviations from these properties and characteristics can bring about inferior fluid performance.

As is demonstrated by Table I, the functional fluid compositions incorporating heavy water are effective in inhibiting and controlling damage to members in contact with such fluids. The effectiveness of heavy water in inhibiting and controlling damage is approximately of the same magnitude as that of water, that is, water which does not contain any isotopes of hydrogen or oxygen. Thus, water itself is eflective in inhibiting and controlling damage in mechanical members and to functional fluids. However, the presence of water in functional fluids can bring about an adverse side effect which under certain conditions increases acid build-up. Such acid build-up can result in increased chemical reactivity of the fluid whereby mechanical parts are chemically attacked. As a consequence of the increased chemical reactivity of the fluid, pitting, wear and alterations of the close tolerances of the mechanical members can occur. Thus, premature overhaul of mechanical parts and increased chemical reactivity can be a direct consequence of acid build-up. It is therefore of particular importance that acid build-up be controlled so as to extend the useful life of the fluid in a functional fluid system. As is significantly demonstrated by Table II, the incorporation of heavy water in a functional fluid brings about not only control and inhibition of damage but in addition gives approximately a 54% reduction in acid build-up of the same base stock which incorporates water at the same concentration. Thus, while both water and heavy water inhibit and control damage, heavy water improves and controls acid build-up to a far greater extent. This improvement, utilizing the compositions of this invention, provides functional fluids with extended periods of operational use wherein acid build-up and damage is inhibited and controlled. As a result of the excellent control of damage and acid build-up in functional fluids which incorporate heavy water, lubrication of gas turbine engines is obtained over extended periods of time. Thus, this invention also relates to a novel method of lubricating gas turbine engines which comprises maintaining on the bearings and other points of wear a lubricating amount of a composition of this invention.

As a result of the execllent inhibition and control of damage utilizing the functional fluid compositions within the scope of this invention, improved hydraulic pressure devices can be prepared in accordance with this invention which comprise in combination a fluid chamber and an actuating fluid composition in said chamber, said fluid comprising a mixture of one or more of the base stocks hereinbefore described and a minor amount, suflicient to inhibit damage, of heavy water. In such a system, the parts which are so lubricated include the frictional surfaces of the source of power, namely the pump, valves, operating pistons and cylinders, fluid motors, and in some cases, for machine tools, the ways, tables and slides. The bydraulic system may be of either the constant-volume or the variable volume type of system.

The pumps may be of various types, including centrifugal pumps, jet pumps. turbine vane, liquid piston gas compressors, piston-type pump, more particularly the variable-stroke piston pump, the variable-discharge or variable displacement piston pump, radial-piston pump, axial-piston pump, in which a pivoted cylinder block is adjusted at various angles with the piston assembly, for example, the Vickers Axial-Piston Pump, or in which the mechanism which drives the pistons is set at an angle adjustable with the cylinder block; gear-type pump, which may be spur. helical or herringbone gears, variations of internal gears, or a screw pump; or vane pumps. The valves may be stop valves, reversing valves, pilot valves, throttling valves. sequence valves, relief valves, servo valves, non-return valves, poppet valves or unloading valves. Fluid motors are usually constantor variable-discharge piston pumps caused to rotate by the pressure of the hydraulic fluid of the system with the power supplied by the pump power source. Such a hydraulic motor may be used in connection with a variable-discharge pump to form a variable-speed transmission. It is, therefore, especially important that the frictional parts of the fluid system which are lubricated by the functional fluid be protected from damage. Thus. damage brings about seizure of frictional parts, excessive wear and premature replacev ment of parts.

The fluid compositions of this invention when utilized as a functional fluid can also contain dyes, pour point depressants, metal deactivators, acid scavengers, antioxidants, defoamers in concentration suflicient to impart antifoam properties, such as from about 10 to about 100 parts per million, viscosity index improvers such as polyalkylacrylates, polyalkylmethacrylates, polycyclic polymers, polyurethanes, polyalkylene oxides, polyalkylenes, polyphenylene oxides and polyesters, lubricity agents and the like.

It is also contemplated within the scope of this invention that the base stocks as aforedescribed can be utilized singly or as a fluid composition containing two or more base stocks in varying proportions, The base stocks can also contain other fluids which include in addition to the functional fluids desired above fluids derived from coal products, and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc., and the mixtures thereof), alkylene oxide-type polymers (e.g., propylene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerizing the alkylene oxide in the presence of water or alcohols, e.g., ethyl alcohol, alkyl benzenes, (e.g., monoalkyl benzene such as dodecyl benzene, tetradecyl benzene, etc.), and dialkyl benzenes (e.g., n-nonyl Z-ethyl hexylbenzene); polyphenyls (e.g., biphenyls and terphenyls), halogenated benzene, halogenated lower alkyl benzene, monohalogenated diphenyl ethers (e.g., fluoro-, bromoand chlorohalogenated benzenes such as m-dibromobenzene, fluoro-, bromoor chlorohalogenated lower alkyl-substituted benzene and bromoand chloromonohalogenated diphenyl ether), trialkyl phosphine oxides, diarylalkyl phosphonates, trialkyl phosphonates, aryldialkyl phosphonates and triaryl phosphonates.

While this invention has been described with respect to various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

1. A composition consisting essentially of (A) a major amount of a phosphorus-containing base stock represented by the formula 2)b in wherein Y is selected from the group consisting of oxygen, and

Ra all,

Y is selected from the group consisting of oxygen, and

and Y is selected from the group consisting of oxygen, and

R, R R R R and R are each selected from the group consisting of alkyl and alkoxyalkyl having from 1 to 18 carbon atoms, aryl and alkaryl having from 6 to 10 carbon atoms and members of the above groups substituted with halogen and a, b, and c are whole numbers having a value of 0 or 1 and the sum of a+b+c is from 1 to 3, and mixtures of such phosphorus-containing base stocks and (B) a damage inhibiting amount of from about 0.005 to about 5 volume percent of a material selected from the group consisting of HOD, D 0, HO D, D 0 HO D, D 0 and mixtures thereof.

2. A composition of claim 1 wherein (B) is D 0.

3. A composition consisting essentially of (A) a major amount of a phosphorus-containing base stock represented by the structure wherein Y is oxygen or Y is oxygen or R, R R R R and R each are selected from the group consisting of alkyl and alkoxyalkyl having from 1 to 18 carbon atoms, aryl and alkaryl having from 6 to 10 carbon atoms and members of the above group substituted by halogen and b and c are whole numbers having a value of 0 or 1 and the sum of b and c is from 1 to 3 and mixtures thereof, and (B) a damage inhibiting amount of from about 0.005 to about 5 volume percent of a material selected from the group consisting of HOD, D 0, HO D, D 0 HO D, and D 0 I 4. A composition of claim 3 wherein (B) is D 0. 5. A composition consisting essentially of (A) a major amount of a phosphorus-containing base stock represented by the formula l? i R-(Y)PN-R2 wherein Y is oxygen or R, R R R R and R are each selected from the group consisting of alkyl and alkoxyalkyl having from 1 to 18 carbon atoms, aryl and alkaryl having from 6 to 10 carbon atoms and members of the above groups substituted with halogen, and mixtures of said base stocks and (B) a damage inhibiting amount of from about 0.005 to about 5 volume percent of a material selected from the group consisting of HOD, D 0, HO D, D 0 HO D, D 0 and mixtures thereof.

6. A composition of claim 5 wherein (B) is D 0.

7. A composition consisting essentially of (A) a major amount of a phosphorus-containing base stock represented by the formula )u i)c z 2)!) in wherein Y is selected from the group consisting of oxygen, and

Y is selected from the group consisting of oxygen, and

R4 z z and Y is selected from the group consisting of oxygen, and

its

R. R R R R and R are each selected from the group consisting of alkyl and alkoxyalkyl having from 1 to 18 carbon atoms, aryl and alkaryl having from 6 to 10 carbon atoms and members of the above groups substituted with halogen, and a. b, and c are whole numbers having a value of or 1 and the sum of a+b+c is from 1 to 3, and mixtures of such phosphorus-containing base stocks and (B) a viscosity index improver selected from the group consisting of polyalkylacrylates and polyalkylmethacrylates and (C) a damage inhibiting amount of from about 0.005 to about volume percent of a material selected from the group consisting of HOD, D 0, HO D, D 0 HO D, D 0 and mixtures thereof.

8. A composition consisting essentially of (A) a major amount of a phosphorus-containing base stock represented by the formula R, R R R R and R are each selected from the group consisting of alkyl and alkoxyalkyl having from 1 to 18 carbon atoms, aryl and alkaryl having from 6 to carbon atoms and members of the above groups substituted with halogen, and mixtures of said base stocks and (B) a viscosity index improver selected from the group consisting of polyalkylacrylates and polyalkylmethacrylates and (C) a damage inhibiting amount of from about 0.005

to about 5 volume percent of a material selected from the group consisting of HOD, D 0, HO D, D 0 HO D, D 0". and mixtures thereof.

9. A method for controlling damage to mechanical members in a hydraulic system which comprises employing as the hydraulic fluid in said system a composition of claim 1.

10. A method for controlling damage to mechanical members in a hydraulic system which comprises employing as the hydraulic fluid in said system a composition of claim 5.

11. A method for controlling damage to mechanical members in a hydraulic system which comprises employing as the hydraulic fiuid in said system a composition of claim 6.

12. A method for controlling damage to mechanical members in a hydraulic system which comprises employing as the hydraulic fluid in said system a composition of claim 7.

13. A method for controlling damage to mechanical members in a hydraulic system which comprises employing as the hydraulic fluid in said system a composition of claim 8.

14. A composition of claim 2 wherein a, b, and e have a value of l.

15. A composition of claim 14 wherein R, R and R are each selected from alkyl having from 2 to 12 carbon atoms and aryl, alkaryl, haloaryl, and haloalkaryl having from 6 to 10 carbon atoms and Y Y and Y are oxygen.

16. A composition of claim 15 wherein R, R and R are each selected from alkyl having from 2 to 8 carbon atoms and aryl, alkaryl, and haloaryl having from 6 to 8 carbon atoms.

17. A composition of claim 16 wherein R is phenyl and R and R are butyl.

18. A composition of claim 5 wherein Y is oxygen and R R R and R are each alkyl having from 1 to 8 carbon atoms.

19. A composition of claim 18 wherein R is selected from aryl, haloaryl, and alkaryl having from 6 to 8 carbon atoms and R R R and R are alkyl having from 1 to 6 carbon atoms.

References Cited UNITED STATES PATENTS 2,379,855 7 "1945 Allderdice 252-76 1,470,792 5/1949 Schlesinger et al 25278 3,513,097 5/1970 Langenfeld 252-78 2,934,501 4/1960 Moreton 252-78 3,218,265 11/1965 Rink et a1. 252- X 3,324,036 6/1967 Shiflier 252-78 X OTHER REFERENCES The Condensed Chemical Dictionary, 6th edition, Reinhold, 1956, p. 561.

LEON D. ROSDOL, Primary Examiner H. A. PITLICK, Assistant Examiner U.S. Cl. X.R. 

